1. Field of the Invention
The invention lies in the field of the further processing of printed products, and relates to a method and to a device, which serve for the serial supplying, opening and depositing of folded printed products.
Folded printed products comprise a fold-edge and an open edge located opposite the fold-edge. They comprise two product parts which are connected to one another at the fold-edge, and the folded printed product can be opened by moving the two product parts apart, starting from the open edge.
2. Description of Related Art
According to the state of the art, folded printed products are supplied one after the other, for example to further processing, wherein the printed products are conveyed with trailing fold-edges (e.g. clamped in between two press belts), and are then pushed downwards out of a clamping gap (e.g. nip between two opposite deflection rollers of the press belts) one after the other and with their open edges facing forwards. During exit from the clamping gap, each printed product is at least partly opened (e.g. by fixing at least one product part in the region of the periphery of the deflection rollers) and each opened printed product falls, as soon as its fold-edge has left the clamping gap, onto a support (e.g. a saddle-like support with a saddle line aligned parallel to the clamping gap). Supported by the support, the printed product is then conveyed onwards (e.g. by a suitable movement of the support), and is processed further as the case may be (e.g. brought together with other folded printed products and/or bound).
Folded printed products being folded off-center, so that one product part protrudes at the open edge over the other product part (gripper fold), are usually opened by gripping the protruding product part, which exits first from the clamping gap, at its leading edge using a gripper, and separating it from the other product part. As soon as the leading edge of the protruding product part is sufficiently distanced from the other product part, it becomes possible to grip the other product part at its leading edge and to move it in the opposite direction for further opening the printed product. Depending on the intrinsic stiffness of the two product parts and on the adhesion between the two product parts, printed products can be opened without problem, even if the leading edge of the non-protruding product part is not gripped. Folded printed products which only consist of a single folded sheet, or printed products which are folded several times, may also be opened during exit from the clamping gap with the help of suction devices. Such suction devices act on the outer side of at least one of the product parts and are able to open such products whether they are folded off-center or not.
For further processing of printed products following the supplying, opening and depositing as briefly described above, without problem and in a precise manner the products are usually first aligned, because it is not possible to deposit the printed products on the supports with the necessary precision and each one in exactly the same manner. For printed products deposited on saddle-like supports it is particularly important that the fold-edge of each deposited printed product lies exactly above the saddle line of the support and is aligned to this saddle line. If for example a plurality of folded sheets is successively deposited on a saddle-like support and is then stapled through the fold-edges of the sheets still resting on the saddle-like support, precise stitching is possible only if the fold-edges of all sheets are lying exactly on one another and exactly above the saddle line.
An exact deposition of the printed products becomes particularly difficult when the supports are conveyed below the clamping gap in an essentially continuous manner and the clamping gap is stationary. In such a case, the saddle line moves relative to the clamping gap, whilst a printed product falls towards the support in an essentially unguided manner to be deposited on the support.
The mentioned problem is less pronounced in devices in which the printed products are not pushed out of a clamping gap, but are supplied each being held by a gripper at its fold-edge. This is due to the fact that using the grippers, it is easier to bring the printed products in a guided manner closer to the supports and let them follow the supports better, than is possible using a clamping gap. On the other hand, supply of the products with grippers asks for opening means which are substantially independent of the supply means in order to be able to guide the free edges of the product parts. This renders the device complicated, in particular when the products to be processed are highly flexible and light (i.e. easily influenced by draughts).
In order to be able to achieve the above mentioned high depositing precision also with the clamping gap method, the publication of DE-19638448 (Grapha-Holding) suggests to pivot the saddle-like supports, on being conveyed substantially continuously past below the clamping gap, about an axis being parallel to the saddle line and the clamping gap, and being situated below the saddle line. This pivoting is controlled in such a manner that the saddle line remains below the clamping gap for a longer time, so that the folded printed product can fall onto the support during this time. The disadvantage of this measure lies in the fact that although the alignment of the saddle line and the clamping gap remains unchanged over a certain time, the distance between the saddle line and the clamping gap and in particular the spatial orientation of the saddle-like support change due to the pivoting, which may lead again to inaccurate deposition.